The sunglass industry has been making curved lenses since the early 1900's through molding, casting or forming. The materials that have been used are glass, CR39, Polycarbonate, Polyurethane, acrylic and more. The technology in the curved eyewear market for sunglasses has greatly improved since the mid 1990's.
Polarized sunglasses have also been around for a long time and some of the first polarized filters were made in the early 1900's by Edwin H. Land, the founder of the Polaroid Corporation. Mr. Land developed a way to spread liquid quinine crystals with a north and south polar axis onto thin film by using magnets. Later the film process was improved by using stretched PVA Polyvinyl alcohol soaked in iodine. Solid, stable pieces of film were later used for different needs, such as sunglass lenses. There have been many techniques used to laminate polarized film between two surface materials. One of the main challenges is that sunglass frames are made from metal.
When a sunglass lens is cut and installed into a metal sunglass frame, the lens can occasionally get caught on the edge causing the lens to delaminate and eventually completely separate from the two substrates. It is common for sunglass lenses to delaminate due to extreme heat exposure, wherein the glue used in the lamination process becomes detached.
One of the most important components of polarized film is the quality and thickness of the end product. Polarized film is graded by its filtration and its efficiency. The efficiency is done by taking two pieces of polarized film and crossing them in front of each other. Then a light meter is set between the material to measure how much light passes through. The best result is 100% efficiency, which means 0 percent of light passes through the two films when crossed at a perfect 90 degree angle.
There is a need in the art to create a polarized filter from a liquid crystal and, in addition, control the thickness and apply it to a curved surface.